The progression of some disease conditions may be ascertained by structural changes in anatomical structures. For example, expansion of brain ventricles in patients with Alzheimer's disease (AD) occurs as a consequence of brain tissue loss with disease progression. Measuring ventricular size over time is useful for monitoring disease progression and may be used, for example, to assess the therapeutic effects of drugs or other treatments that prevent or slow disease progression.
It is known that ventricular size can be measured using Magnetic Resonance Imaging (MRI) techniques, including automated voxel-based morphometric (VBM) approaches, manual or semi-automated volumetric segmentation algorithms, and linear measurements. However, these methods can be affected by image quality, take a long time, and/or be difficult to reproduce.
A technique for measuring changes in volume of cerebral structures, which could be used for measuring changes in ventricular size, is described in: The boundary shift integral: an accurate and robust measure of cerebral volume changes from registered repeat MRI; Freeborough, P. A.; Fox, N. C.; IEEE Transactions on Medical Imaging, Volume 16, Issue 5, October 1997 Page(s):623-629 (which is hereby incorporated by reference in its entirety). An example of images used in this process are illustrated in FIG. 6.
Another technique, called Brain Parenchymal Fraction (BPF) was also described in Rudick R A, Fisher E, Lee J C, et al. Brain atrophy in relapsing multiple sclerosis: relationship to relapses, EDSS, and treatment with interferon beta-la. Mult Scler2000; 6:365-372 (which is hereby incorporated by reference in its entirety).